Defects in an argument

2. Fallacies are defects in an argument
which cause an argument to be invalid,
unsound or weak.

3. An appeal to ignorance occurs when one person uses another
person’s lack of knowledge on a particular subject as
evidence that their own argument is correct.
For example: “You can’t prove that there aren’t
Martians living in caves under the surface of Mars,
so it is reasonable for me to believe there are.”

4. This type of fallacy is also referred to as Argumentum ad
Verecundia (argument from modesty). In this case, rather
than focusing on the merits of an argument, the arguer will
try to attach their argument to a person of authority in an
attempt to give credence to their argument.
For example: “Well, Isaac Newton believed in
Alchemy, do you think you know more than Isaac
Newton?”

5. This type of appeal is when someone claims that an idea or
belief is true simply because it is what most people believe.
For example: “Lots of people bought this album, so it
must be good.”

6. Sometimes called "guilt by association," this occurs when
someone links a specific idea or practice with something or
someone negative in order to infer guilt on another person.
For example: “Hitler was a vegetarian, therefore, I
don’t trust vegetarians.”

7. Also known as Argumentum ad Hominem (argument against
the man), this is quite a common occurrence in debates and
refers to a person who substitutes a rebuttal with a personal
insult.
For example: “Don’t listen to Eddie’s arguments on
education, he’s an idiot.”

8. Also referred to as Circulus in Probando, this fallacy is when
an argument takes its proof from a factor within the
argument itself, rather than from an external one.
For example: “I believe that Frosted Flakes are great
because it says so on the Frosted Flakes packaging.”

9. Otherwise known as Cum Hoc Ergo Propter Hoc, this is a
fallacy in which the person making the argument connects
two events which happen sequentially and assumes that one
caused the other.
For example: “I saw a magpie and ten minutes later, I
crashed my car, therefore, magpies are bad luck.”

10. Sometimes referred to as Bifurcation, this type of fallacy
occurs when someone presents their argument in such a way
that there are only two possible options.
For example: “If you don’t vote for this candidate,
you must be a Communist.”

11. A fallacy where in someone asserts a conclusion that does not
follow from the propositions.
For example: “All Dubliners are from Ireland. Ronan
is not a Dubliner, therefore, he is not Irish.”

12. Assuming that a very small action will inevitably lead to
extreme and often ludicrous outcomes.
For example: “If we allow gay people to get married,
what’s next? Allowing people to marry their dogs?”

13. bases an inference on too small a sample, or on an
unrepresentative sample. Often, a single example or instance
is used as the basis for a broader generalization.
example: All of those movie stars are really rude. I
asked Kevin Costner for his autograph in a
restaurant in Westwood the other evening, and he
told me to get lost.

14. A fallacy very similar to slippery slope, which involves taking
an argumentative claim or assertion to its extreme, even
though the arguer does not advocate the extreme
interpretation. The difference between the two fallacies is that
appealing to extremes does not necessarily involve a
sequence of causal connections.
example: Husband to ex-wife: Well, if you want to
be completely fair about dividing everything up, you
should get one of my testicles and I should get one of
your breasts!

15. This fallacy consists of offering a poorly supported claim
about what might have happened in the past or future if
circumstances or conditions were other than they
actually were or are. The fallacy also involves treating
hypothetical situations as if they were fact.
EXAMPLE: If Hitler had not invaded Russia and
opened up two military fronts, the Nazis would
surely have won the war.